Communication problems with MegaTune using USB - RS232 converters are common.
It all comes down to how the converters work due the vast speed differences between the 2 interface types.
As USB is sooo much faster, what the adapter does is store a bunch of data internally (buffer) and then transmit it all in one go either when the buffer is full or after a time out. This buffering is what is messing stuff up.
The RS232 setting you gave are right and flow control should be set to off.
To fix the problem may needs admin right on your laptop, so as it is a work machine that may be an issue.
What you need to do is go into the device manager, select the USB com4 port, go into properties, then port settings, then Advanced, then reduce the buffer size (both if receive and transmit are listed seperately) to minimum (1msec).
This will then mean that as the ECU send or receives data it will get dealt with by the PC straight away instead of waiting for a load to get stored up then sent in one great big chunk.
Hilly
